Solar Shed

Chronicles of my experiments with solar power and automation in our shed


Lessons Learned:

Lead acid batteries are not worth it. While temptingly cheap, they are not nearly as powerful as lithium batteries, expel hydrogen gas, and can spill acid. I did manage to run the air conditioner with 2 large 12V lead acid in the sun, but without sun its too much constant current.

Read the fucking manual. Just because cheap charge controllers will accept just about any solar panel doesn’t mean better charge controllers will also. Renogy DC-to-DC has an unusually low voltage ceiling of 25V, had to buy one of their panels before it would work reliably.

Insulate. Air conditioner cools 10 degrees lower than the outside max without insulation, so it still sucks on 100+ degree days.

Diodes do not work in parallel. Tried (2) 20A diodes in parallel for 30A of current, all the power went through a single diode. This is not at all intuitive to me.

Flexible panels break fast. I assume due to high heat.

Supercaps cannot be initially charged with any 12V battery charger, mine thought it was a dead short. Ended up having putting halogen lamp as load in series.

Heated batteries are needed in sub 0 degree winter environments, chargers will not charge lithium on very cold mornings.

You can put 24V loads onto a singe or parallel sets of panels, using 24V fan for charge controller this way so it is only on when the sun is out (when it needs it)

Current configuration:

  • (6) 100W Mono panels in series-parallel connected to 40A MPPT charge controller, charging 150Ah battery
  • (2) 100W Mono panels in series connected to 20A MPPT charge controller, charging 50Ah battery
  • (1) 100W Mono panel connected to 50A MPPT DC-to-DC charge controller, connected to both battery banks, charges both ways
  • (1) PV Combiner box with diodes
  • (1) 1500W Inverter – pure sine
  • (1) 410W Window mounted air-conditioner
  • (1) 15A DC DP-DT Circuit Breaker
  • (1) 25A DC DP-DT Circuit Breaker
  • (1) 32A DC DP-DT Circuit Breaker
  • (1) Inline power meter with shunt and display
  • (1) 12VDC Switchbox
  • (1) 24VDC Switchbox
  • (1) 5-24VDC Timer Relay
  • (1) 24VDC cooling fan